Fred Saar wrote:
> 
> We have received an inquiry, from one of our customers, questioning a
> rework method, that we regularly use when incorporating certain types of
> engineering changes on Printed Circuit Assemblies.  This method is used when
> it is necessary to isolate a surface mount IC lead and add a connection to
> that isolated lead. It consists of the following method:
> 
> 1. Carefully desolder the lead from the pad on the board and reform the IC
> lead so that it will not touch the pad.
> 
> 2.  Lap solder a 30 ga solid wire to the lead mentioned in step 1 and
> route the wire to the appropriate connection on the board.
> 
> My question is although IPC-R-700C procedure 5.2.4 (pg. 185) allows lap
> soldering of wires to surface mount leads,  are there any
> documented procedures for allowing a surface mount lead to be lifted from a
> pad, reformed so that it does not touch the pad and lap soldering a wire
> to it?  We would like to be able to defend our position, to the customer
> with documentation that supports this type of rework method.
> 
> I'm looking forward to any comments, ideas or documents related to this issue.
> 
> Thanks,
> 
> Fred Saar
> 
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Fred, What you are refering to is an Engineering Change (EC) procedure 
and is internal to most of the companies doing the rework. 

You may , however, check for the following to staisfy your customer:

1. While reforming the lead after desoldering, inspect for damage at the 
lead to component body interface for crack, delam etc.
2. Are you providing stress relief to the lap soldered wire joint? 
For example by tacking the wire.

The trick is to avoid possibility of surprise field fails.
-- 
Pratap Singh
Tel./Fax: 512-255-6820
e-mail: [log in to unmask]


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